Normal sinus rhythm of the heart begins with an electrical impulse generated by the sinus node that propagates across the right and left atria (the two small upper chambers of the heart) to the atrioventricular node. Atrial contraction leads to pumping blood into the ventricles in synchronization with the electrical pulse.
The term “atrial fibrillation” is a type of cardiac arrhythmia, or irregular heartbeat, in which the atria fail to contract effectively. During atrial fibrillation, disorganized electrical conduction in the atria causes rapid uncoordinated contractions, resulting in sub-optimal pumping of blood into the ventricle. The atrioventricular node may receive sporadic electrical impulses from many locations throughout the atria, instead of only from the sinus node. This electrical confusion may overwhelm the atrioventricular node, producing an irregular and rapid heartbeat. Consequently, blood may pool in the atria and increase a risk for blood clots.
While there are numerous variations of atrial fibrillation with different causes, they all involve irregularities in the transmission of electrical impulses through the heart. As a result, the heart does not pump the blood properly, and it may pool and clot. If a blood clot forms and moves to an artery in the brain, atrial fibrillation can lead to stroke.
The major risk factors for atrial fibrillation include age, coronary artery disease, rheumatic heart disease, hypertension, diabetes, and thyrotoxicosis. Atrial fibrillation affects 7% of the population over 65 years of age, and is also associated with increased risks of congestive heart failure and cardiomyopathy, which warrant medical attention and treatment. Atrial fibrillation is the most common sustained heart rhythm disorder and increases the risk for heart disease and stroke, both leading causes of death in the United States.
Diagnosis and treatment of arrhythmias and atrial fibrillation may involve mapping or otherwise identifying and characterizing the electrical activity of the relevant anatomy, such as the cardiac tissue of the atria. Some tissues, such as those in the heart, have cells with a measurable internal voltage difference that may be useful in locating and mapping electrical signals. In particular, contact with positive pressure produces a monophasic action potential signal, which may be used to map proper and improper electrically functioning areas.
After mapping, tissue ablation may be used in various medical procedures to treat patients, such as to stop improper electrical propagation through the tissue in patients with an arrhythmia. Various ablation techniques have been proposed to treat atrial fibrillation.